For packaging an electronic device on a substrate, there is known a method of forming a bump ball by Au wire or the like, on a circuit pattern on the substrate, mounting an electronic component thereon, and adhering the electronic component to the circuit pattern, along with establishing electrical connection therebetween by heating and ultrasonic irradiation. There is also known a method of applying a material such as solder paste to the circuit pattern on the substrate, mounting the electronic component thereon, and adhering the electronic component to the circuit pattern, along with establishing electrical connection therebetween by heating and melting the solder.
There is widely known a method for forming a circuit pattern by copper-foil masking followed by etching. This method is, however, complicated in a production process and time consuming, and also expensive production equipment is required. In recent years, a technical field referred to as printed electronics is studied actively, where a circuit pattern is formed by printing, in order to simplify the production process and to reduce cost of the production equipment.
By way of example, in the Patent Document 1, there is disclosed a technique where a non-conductive film containing copper nanoparticles is deposited by using a printer such as an ink jet printer, and thus formed film is exposed to light from above, thereby fusing the copper particles, and then a conductive circuit is formed.